The field of the present invention is air operated pumps.
U.S. Pat. Nos. 8,360,745; 7,399,168; 7,063,516; RE38,239; U.S. Pat. Nos. 6,435,845; 6,357,723; 6,257,845; 5,957,670; 5,169,296; 4,247,264 disclose air driven and air controlled pumps. Actuator valves used in such pumps are also disclosed in the foregoing and are specifically addressed in U.S. Pat. Nos. 8,047,222; 7,125,229; 6,102,363; 4,549,467.
Conventional designs of the foregoing air-driven pumps include pump units, each including a pump chamber, an air chamber and a pumping member between the pump chamber and the air chamber. The pumping members are powered by alternating air pressure and venting to and from the air chamber to stroke back and forth to pump material through the pump chambers. These members may be pistons with annular seals sliding within a cylinder or diaphragms fixed about their periphery and attached to central pistons. U.S. Pat. No. 8,047,222 discloses a recent diaphragm with an integral rigid piston. The air-driven pumps typically have the air chambers to either side of an air valve to facilitate coupling the pumping members together by a shaft extending through the air valve and attached to the pistons.
The air valves for these pumps operate using pilot valve systems that sense pump position or other criteria and initiate shifting of directional control valves to alternate air pressure and venting to and from the air chambers. A pilot system shifting a directional control valve may use a pilot valve associated with the shaft attached to the pumping members to sense end of stroke. Alternatively, a valve may be associated with a pilot shaft, separate from the shaft attached to the pumping members, with probes extending into each air chamber. Another format may use separate valves, each with a probe extending into an air chamber, to provide the pilot function. Such pilot systems actuate the control valves through pressure surfaces on the control valve elements. Alternatively, a solenoid system or solenoid valve system driven by a timer or controller may be used. U.S. Pat. No. 5,378,122 discloses an air driven pump which is controlled by a solenoid that times shifts independently of the position of the pump in its cycle. U.S. Pat. No. 7,517,199 discloses an air driven pump which is controlled by an electronic controller.
The directional control valves of such systems which alternate air pressure and venting to and from the air chambers may be directly driven by an outside means, such as a solenoid, to shift between positions or may be pneumatically driven by a pilot valve such as discussed above. Two types of spool valves are common. One employs a balanced spool with equal piston areas to power the shifting. This type is disclosed in U.S. Pat. Nos. 4,549,467 and 6,102,363. A second common type employs an unbalanced spool with unequal piston areas to power the shifting. This type is disclosed in U.S. Pat. Nos. 7,125,229 and 8,047,222.
The disclosures of each of the aforementioned U.S. Patents in the above Background are incorporated herein by reference in their entireties.